Paper machinery



Nov. .21, 1961 J. H. MARTINDALE 3,009,656.

PAPER MACHINERY Filed June 16, 1958 FIG-8 4 INVENTOR. JAMES H.MART|NDALEATTORNEYS United States hater-it 3,009,656 Patented Nov. 21, 1961 fine3,069,656 PAPER MACHINERY James H. Martindale, Middletown, Ohio,assignor to The Black-Ciawson Qompauy, Hamilton, Ohio, a corporation of()hio Filed June 16, 1958, Ser. No. 742,332 4 Claims. (Cl. 241-46) Thisapplication relates to pulping apparatus for liquid slurry stocks suchas paper making stock.

The invention has special relation to pulping apparatus of the typewherein the stock to be pulped is contained in a tub which is providedwith a rotor or impeller mounted in the bottom thereof for rotation on avertical axis causing outward circulatory movement of the stock in agenerally vo-rtical pattern and which is also provided with an upwardlyand outwardly inclined screen located generally in the path of the stockdischarged by the impeller and controlling the passage of the pulpedparticles to the outlet of the tube. Pulping apparatus of this generaltype is employed in both batch and continuous operations, and theinvention is equally applicable toboth types of operation.

It is a primary object of this invention to provide pulping apparatus ofthe above general type wherein the impeller is of novel and improvedstructural characteristics which not only give increased assuranceagainst clogging of the screen but also make it possible to obtainincreased efiiciency of operation with screens having substantiallysmaller perforations therein than have customarily been used.

A further object of the invention is to provide pulping apparatus asoutlined above wherein the improved operational characteristics areobtained by a novel construction and mode of operation of the impellerwhich effect continuous cleaning of the screen perforations by creatinga periodic pulsing action effective on the upper surface of the screen.

It is a specific object of this invention to accomplish the purposesoutlined above by the provision of a pulping impeller which incorporatesone or more special blades of such structure and operative relationthereto that as the impeller rotates, each blade causes a wave of stockto sweep outwardly along the upper surface of the screen andsubstantially parallel therewith at a high velocity creating a backpressure through the perforations of the screen effective to dislodgeany particles tending to dwell on or in these perforations.

Additional objects and advantages of the invention will be apparent fromthe following description, the accompanying drawing and the appendedclaims.

In the drawing FIG. 1 is a view partly in side elevation and partlybroken away in vertical section showing pulping apparatus embodying animpeller constructed in accordance with the invention;

FIG. 2is a plan View of the impeller in FIG. 1 and a fragment of theassociated screen or extractor plate;

FIG. 3 is an enlarged detail view in plan through one of the componentparts of the impeller of FIG. 2 including oneof the special bladesthereon;

FIG. 4 is a fragmentary elevational view taken as indicated by the lineM4 of FIG. 3;

FlGS. 5-8are fragmentary sections taken as indicated by the sectionlines 5-5, 66, 77 and 8-45 respectively of FIG. 4; and

FIG. 9 is a fragmentary section taken as indicated by the line 9-9 ofFIG. 2.

Referring to the drawing, which illustrates a preferred embodiment ofthe invention, FIG. 1 shows pulping apparatus which is generally of theconstruction disclosed in Martindale Patent No. 2,371,837, issued March20, 1945, to the assignee of this application. This pulper includes atub or vat having a cylindrically extending upper wall portion 10, aninwardly tapered lower wall portion 11 and a bottom wall 12, and it iscarried by supports 13 of anysuitable character. Arranged below the tubis a gear drive 15 shown as driven by a pulley 16 from a suitablylocated motor (not shown), and the gear drive 15 drives a vertical shaft17 which supports an impeller 20 for rotation centrally of the bottomportion of the tub.

In operation, the impeller 2i provides an effective circulationoutwardly and then upwardly along the outer portions of the tub in agenerally vortical pattern providing a return flow towards the impeller,as indicated by the arrows in FIG. 1, and stationary guide plates 21 aremounted on the wall portion 11 to guide the upward flow of the partially.pulped stock. Adjacent the bottom of the tub is an annular chamber orcompartment 22 partitioned from the space above the impeller by aperforate screen or extractor plate 215 of frustoconical form whichpermits the passage to the compartment 22 of pulped particles which havebeen suificie-ntly reduced in size to pass through the perforations ofthis screen 25. This pulped stock may be withdrawn from the compartment22 continuously or batch-wise, by way of the conduit 26 and controlvalve 27.

The present invention is concerned with the fact that it is possibleforincompletely pulped particles to dwell on or partially in theperforations in the screen 25 and thereby to cause partial or completeclogging of the screen. This result is particularly undesirable in batchpulping operations, since it has a definite tendency to delay, or evento stop, dumping of the contents of the tub in view of the fact thatwhen dumping begins, there is a maintained drain-age force through thescreen wall tending to hold clogging particles in place. It isaccordingly the purpose of this invention to provide an impeller 20 ofspecial characteristics providing positive assurance against dwelling ofoversized particles on the screen in such manner as to cause cloggingthereof.

The impeller 29 includes a main supporting plate 30 having a pluralityof segments 31 bolted on the upper surface thereof around its outerperiphery, and these segments 31 each include one or more upstandingimpeller vanes 32 arranged tangentially of the axis of the impeller insuch manner that as the impeller rotates in the direction ofv the arrow33, the stock is discharged outwardly of the impeller toward the screen25 in the general pattern already described in connection with segmentalsimilar to the segments 31 and each also including one pulping vane 32The blades 40 areso constructed and arranged with respect to the balanceof the impeller and the screen 25 that as the impeller rotates, eachblade 40- causes 'a wave of stock to' be directed upwardly along thesurface of the screen 25 in 'a 5 7 direction closely approachingparallelism with the screen and at a substantially, higher velocity thanthe discharge from the vanes 32. The result of these conditions is thatas this high velocity wave crosses the screen 25', it creates an upwardor back pressure through the perforations in the screen tending todislodge any clogging par *tic les for further upward travel into theinterior of the tub. In addition, since this wave is of short elfectivewidth, it rotates around the tub and is followed by pressure in theopposite direction as the stock returns behind it in opposition to theback pressure. Thus as each of these high velocity waves rotates aroundthe tub, it creates an effective pulsating action with respect to theperforations in the screen 25, which comprises essentially a temporaryupward suction through the screen followed by the downward pressureresulting from the static head of stock in the tub.

For preferred results in the practice of the invention, it is importantthat the proper relationship be maintained between the configurations ofthe blade 40 and the perforate screen 25 such that the wave of stockcreated by each blade 40 will be directed upwardly in very nearlyparallel relation with the upper surface of the screen 25, asdistinguished from impinging thereon at materially lesser angles ofincidence as does the discharge from the blades 32, while at the sametime the angle between the direction of this wave and the surface of thescreen 25 should be less than 180. It is therefore desirable to maintainthe radially outer edge of each blade 40 in the same horizontal plane asand very close to the bottom edge of the screen 25, as shown in FIG. 9.In addition, the angle defined by the working surface 44 of the blade 40and the screen 25 in any vertical section should approach but be lessthan 90, as also shown in FIG. 9.

In addition to the angular relationships noted above, each blade 40should include substantially greater working area than each of the vanes32, in order to assure the desired higher velocity for the wave of stockwhich it creates. For example, satisfactory results in this connectionhave been obtained with an impeller whereon the blade 40 reaches amaximum height of 4.625 inches and an overall length of approximately 13inches, in comparison with an overall length of approximately 6 inchesand a maximum height of 1.375 inches for each vane 32. In addition, theblade face 44 is slightly curved in a horizontal plane as shown in FIGS.2-3, to a definite concave configuration which further increases itseffectiveness in the operation of the invention as described above.

Results which have been obtained with pulping apparatus constructed inaccordance with the invention have been outstanding in efficiency in avariety of aspects. Thus operating with pulpers having screens providedwith conventional perforations, clogging has been consistentlyprevented, and therefore the pulping time has been reduced as well asthe dumping time in cases of batch operation. In addition, it has beenfound that these same advantages are obtainable with screens providedwith perforations which are substantially smaller than those customarilyused, for example as small as from A to /8 inch in comparison with holesof 1-inch diameters. A further advantage which results from thesecharacteristics is both that better defibering is obtained within thepulper, since large undefibered particles will not permit it to escapethrough the screen, and also that there is substantially higherretention of undesired trash within the pulper, which in turn decreasesthe amount of screening necessary at subsequent stations in the stockpreparation system.

While the form of apparatus herein described constitutes a preferredembodiment of the invention, it is to be understood that the inventionis not limited to this precise form of apparatus, and that changes maybe made therein without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:

1. In pulping apparatus of the character described including a generallycylindrical tub, an outlet for pulped stock in the lower portion of saidtub, and an upwardly and outwardly inclined annular screen covering saidoutlet, the combination of an impeller mounted for rotation on avertical axis centrally of said screen and including a circular plateforming the body thereof, a plurality of upstanding impeller vanes onthe upper surface of said plate, means for rotating said impeller in thedirection to cause said vanes to produce discharge of the stockoutwardly of said plate toward said screen, a blade on said plateextending in the direction opposite to the direction of rotation of saidplate from a position located inwardly of the periphery of said plate toa position radially beyond the periphery of said plate and closelyadjacent the inner periphery of said screen, said blade being ofsubstantially greater height than said vanes, and the radially outersurface of said blade being inclined upwardly and inwardly with respectto said plate at an angle causing a wave of stock to be directed towardsaid screen at an angle approaching 180 and at a velocity substantiallygreater than the stock discharged by said vanes to effect upwardsweeping of the upper surface of said screen of particles tending todwell thereon accompanied by a pulsating action with respect to theperforations in said screen as said wave moves circumferentially of saidtub.

2. An impeller construction for pulping apparatus of the characterdescribed including a generally cylindrical tub adapted to have animpeller mounted in the bottom thereof for rotation on a vertical axisand having an upwardly and outwardly inclined screen surrounding saidbottom in the path of stock discharged from the periphery of suchimpeller, comprising a circular plate forming the body of said impeller,a plurality of upstanding impeller vanes on the upper surface of saidplate for producing discharge of the stock outwardly of said platetoward said screen, a blade on said plate for causing a wave of stock tobe discharged toward said screen as said impeller rotates, said bladeextending in the direction opposite to the direction of rotation of saidimpeller from a position located inwardly of the periphery of said plateto a position radially beyond the periphery of said plate, said bladebeing of substantially greater height and length than said vanes, andthe radially outer surface of said blade being inclined upwardly andinwardly with respect to said plate at an angle causing said wave ofstock to be directed toward said screen at an angle approaching 180 andat a velocity substantially greater than the stock discharged by saidvanes to effect upward sweeping of the upper surface of said screen ofparticles tending to dwell thereon accompanied by a pulsating actionwith respect to the perforations in said screen as said wave movescircumferentially of said tub.

3. An impeller construction for pulping apparatus of the characterdescribed including a generally cylindrical tub adapted to have animpeller mounted in the bottom thereof for rotation on a vertical axisand having an upwardly and outwardly inclined screen surrounding saidbottom in the path of stock discharged from the periphery of suchimpeller, comprising a circular plate forming the body of said impeller,a plurality of upstanding impeller vanes on the upper surface of saidplate for producing discharge of the stock outwardly of said platetoward said screen, a blade on said plate for causing a wave of stock tobe discharged toward said screen as said impeller rotates, said bladeextending in the direction opposite to the direction of rotation of saidplate from a position located inwardly of the periphery of said plate toa position radially beyond the periphery of said plate, said blade beingof increasing height from the inner to the outer end thereof with themajor portion thereof being of substantially greater height and lengththan said vanes, and the radially outer surface of said blade beingsubstantially flat in section and inclined upwardly and inwardly withrespect to said plate at an angle with respect to the angle ofinclination of said screen which approaches to cause said wave of stockto be directed toward said screen at an angle approaching and at avelocity substantially greater than the stock discharged by said vanesto effect upward sweeping of the upper surface of said screen ofparticles tending to dwell thereon accompanied by a pulsating actionwith respect to the perforations in said screen as said wave movescircumferentially of said tub.

4. An impeller construction for pulping apparatus of the characterdescribed including a generally cylindrical tub adapted to have animpeller mounted in the bottom thereof for rotation on a vertical axisand having an upwardly and outwardly inclined annular screen surroundingsaid bottom in the path of stock discharged from the periphery of suchimpeller, comprising a circular plate forming the body of said impeller,a plurality of upstanding impeller vanes on the upper surface of saidplate for producing discharge of the stock outwardly of said platetoward said screen, a blade on said plate for causing a wave of stock tobe discharged toward said screen as said impeller rotates, said bladeextending in the direction opposite to the direction of rotation of saidplate from a position located inwardly of the periphery of said plate toa position radially beyond the periphery of said plate, said blade beingof increasing height from the inner to the outer end thereof with themajor portion thereof being of substantially greater height than saidvanes, the radially outer surface of said blade being substantially flatin section and inclined upwardly and inwardly with respect to said plateat an angle with respect to the angle of inclination of said screenwhich approaches 90 to cause said wave of stock to be directed towardsaid screen at an angle approaching 180 and at a velocity substantiallygreater than the stock discharged by said vanes to effect upwardsweeping of the upper surface of .said screen of particles tending todwell thereon accompanied by a pulsating action with respect to theperforations in said screen as said wave moves circumferentially of saidtub and saidouter face of said blade having a concavely curvedconfiguration in plan to increase the velocity of said wave of stock.

References Cited in the file of this patent UNITED STATES PATENTS FranceJan. 6, 1954

